Analog to digital converters ("ADCs") are electronic devices which generate a digital signal from an analog input. ADCs serve to bridge the gap between digital signal processing and analog signal processing equipment in many areas including computer I/O interfaces, lab test equipment and consumer goods such as digital audio tape recorders.
ADCs convert their analog input to a digital output according to a mathematic transfer function. Linear, A-law companding and .mu.-law companding are three popular transfer functions known in the art which are widely accepted. Heretofore, ADCs have converted data according to either (1) a linear transfer function, (2) one of the companding functions or (3) either of the companding functions as selected by the user. No known ADC has allowed a user to alternatively convert an analog input into a digital output by a linear or by a companding transfer function. At least two devices have been required to perform all three conversion modes.
Therefore, a need has arisen for an ADC which is operable to convert an analog input into a digital output by either a linear, A-law companding or .mu.-law companding transfer function.